Avocational paleontologist Mark Renz stumbles onto an ancient graveyard of mammoths, mastodons, sloths, horses, llamas, deer, peccaries, saber-toothed cats, jaguars, bears, wolves, snakes and alligators. Was it a major storm, flood, drought or plague that killed so many creatures at once? What signs do scientists look for to determine cause and time of death? What are the ethical considerations for amateurs who come across such a site? Do you keep the bones for yourself, sell them, or donate them to a museum?

Close to 800 field photos offer readers a rare glimpse at the final moments in the lives of these animals.